For a sunglass or sunglass lens to be successful in the high-end sunglass marketplace the product must have good optics and good aesthetics. In the last twenty years sunglass designs, in terms of optics and frames, have advanced significantly. The marketplace is highly competitive and it is very difficult for a new product, using existing methods, designs and know how, to stand out from the rest. The designs and technologies used in the manufacture of sunglasses have been highly perfected and standardized. And, as a result, sunglass types that are successful all share those same basic designs and technologies and, as a result, look substantially alike.
Virtually all sunglass lenses produce a pronounced specular reflection in that they reflect images of their environmental surroundings corresponding to the light that is impinging on the lens, similar to the way light reflects off a windowpane. Specular reflection is the type of reflection seen by a person when looking into a windowpane or a mirror. The described reflection is an inherent byproduct of a typical untreated surface that is optically smooth. When a highly reflective coating, such as a mirror coating, is applied to the surface of an optical lens it simply accentuates the reflective nature of that lens. One of the desirable functions of a sunglass lens among many consumers is that it conceal the wearer's eyes from an observer's point of view. In the case of a lens that does not have a mirror coating, it is dark tint in combination with the natural reflection off the surface of the lens that conceals the eyes of the wearer. Except in the case where a sunglass lens incorporates an encapsulated specular reflecting mirror coating, anti-reflective coatings are seldom placed on the front side of a sunglass lens. This is because it would be much easier for an observer to see through the lens to the eyes of the wearer. In the case of sunglass lenses, anti-reflective coatings are usually only employed on the backside of the lens adjacent the wearer's eyes, in which case the anti-reflective coating serves only to enhance the optics and does nothing to detract or enhance the aesthetic appearance of the lens from an observer's point of view. By placing the anti-reflective coating on the backside only, the reflection off the front of the lens is preserved. For conventional sunglass lenses, specular reflection is normally central to the design objective of the lens. For a sunglass consumer, the fashion choice among lenses is generally limited to lenses that reflect images of their surroundings, minimally or significantly, depending on whether or not they are mirror coated.
Past inventors have attempted to design a lens that departs from what is commonly expected in a sunglass lens by creating a lens that reflects light in a manner that features images of objects, faces, logos, letters or words. These attempts have incorporated reflective coated holographic diffraction patterns, also known as holograms, bas-reliefs, and surface etchings, such as photographic etchings, in a lens construction. Images that have been described in the prior art include faces of people, skulls, worms, eyeballs, and other types of inanimate objects such as monetary coins and nails, as well as logos. Holograms are used to create predetermined light wave interference patterns in reflected light to form the appearance of a desired image. Bas-reliefs and photo etchings are used to create varying shades of light and dark areas in predetermined patterns of reflected light to create a desired image. Other prior art described the use of alternating transparent colors to create the appearance of decorative patterns, such as a star pattern, in reflected light.
U.S. Pat. No. 4,315,665 first formulated the idea of creating a sunglass lens that features decorative images of objects and light patterns in reflected light by encapsulating a reflective coated light diffraction pattern, also known as a hologram, between two optically clear layers. Light diffraction patterns in particular are problematic in that they cause substantial internal reflections. There have been numerous later attempts to create a marketable sunglass type lens that reflects images of objects, faces, and/or logos. U.S. Pat. Nos. 4,934,792 and 5,073,009 describe similar lens constructions employing reflective coated bas-reliefs and photographic etchings to feature images of objects and pictures in reflected light, such as a silver dollar coin or a photographic image. U.S. Pat. No. 6,793,339 describes an etching process to create the appearance of a decorative logo, in combination with specular reflection to create a glossy appearance. Without exception, these prior art examples describe lens constructions that reflect images of objects, faces, logos or words as well as reflect images of environmental surroundings due to specular reflection.
U.S. Pat. Nos. 6,231,183 and 6,719,928, authored by the present inventor, describe a lens that reflects light but reflects almost no image. In this prior art the vast majority of the light being reflected by the lens came from an encapsulated reflective coating contoured by either a brushed surface finish or a matte surface finish. The described surface finish was used to break up reflected light so the reflective coating would not produce a specular reflection that would otherwise be apparent to an observer. Additionally, anti-reflective coatings were applied, primarily to the front surface of the lens. The anti-reflective coatings were employed to remove or substantially reduce the specular reflection coming off of the front lens surface, which would otherwise negate the effect of the matte or brushed finish and the lens construction as a whole. Without the inclusion of the anti-reflective coating, the lens construction would still produce reflections in the form of images because, in addition to light being reflected off the encapsulated reflective coating, a high percentage of light would also be reflected off the optically smooth outer surface of the lens, thus producing a specular reflection similar to that of a window pane or conventional sunglass lens. In most natural lighting conditions, the specular reflection coming from the optically smooth surface would also partially conceal the reflection produced by the reflective coating. This prior art recognized the inherent difficulty of matching refractive indices associated with lens constructions of earlier prior art. In response to these shortcomings, the referenced prior art of the present inventor described a lens construction that incorporated a textured finish with a reflective medium applied thereon encapsulated within a lens construction that guaranteed matched refractive indices in the critical area of the lens construction. It has since been discovered that perfectly matching the refractive indices do not in itself eliminate all of the problems associated with such a lens construction as a whole. The matte finish of the prior art was created as a dull finish having little to no contrast in reflected light. The matte finish was found to have significant limitations in terms of achieving both good optics and good reflective characteristics. The problem with a matte finish is that it diffuses reflected light too much. The term contrast is meant to describe the appearance of light reflected off a surface. If a bright light impinges on a spherical surface having an optically smooth surface finish, a distinct reflection of the incident light reflecting off the surface will appear at a single point on the spherical surface. This is because an optically smooth surface exhibits high contrast. If a similar spherical surface having a surface finish with little or no contrast, such as a matte finish, is highlighted with the same bright light, a large portion of the surface area will be illuminated simultaneously. This is because a matte finish exhibits low contrast. On a matte finish, the contrast is low because reflected light is scattered to a high degree and, because the reflected light is scattered to a high degree, the brightness of the reflection is reduced. It has been found that a surface finish having exceedingly low contrast does not produce a bright enough reflection when encapsulated within a lens construction. As described, the present inventors prior art lens was designed so that the majority of the reflected light comes from the encapsulated reflective medium within the lens. Therefore, if the reflection produced by the reflective medium is not bright enough, light is more easily transmitted from the wearer's side of the lens to an observer's side of the lens. Thus, the majority of the reflection produced by the reflective medium is canceled out, making it easier for an observer to see through the lens to the eyes of the wearer. In an effort to increase its reflectivity, increased amounts of a reflective medium, such as chromium, were applied to the matte finish. In doing so it became evident that there is a limit as to how much reflective medium should be applied to a lens construction, beyond which the optical performance of the lens is degraded. When using metallic reflective mediums, such as chromium or aluminum, increasing the amount of the reflective medium produces a brighter reflection but correspondingly reduces the amount of light capable of being transmitted. In addition to the reflective medium, there is also a light-absorbing element in the form of tint or a polarized film positioned between the reflective medium and the eye of the wearer. In addition to absorbing the bright light of the sun, the light-absorbing element serves to absorb light being reflected off of the reflective medium back toward the eye of the wearer (back reflection). The use of more reflective medium increases the brightness of the resulting reflection, thus requiring a darker tint to attenuate the back reflection. The result of using too much reflective medium is that the lens becomes too dark, which reduces its ability to transmit light. A properly constructed lens of this type requires a balance between the light transmittance level of the reflective medium and the light transmittance level of the light-absorbing element. This is so that the final lens construction will transmit an acceptable amount of light as outlined by the appropriate American National Standards Institute (ANSI) standards for sunglass lenses. If the only objective is to create a surface that reflects bright enough, then an unlimited amount of reflective medium could be applied to the surface finish. When operating within the constraints of an optical lens, however, there are limits as to what can be achieved with a given design such as the matte finish. In this case it proved difficult to achieve an acceptable amount of brightness in reflected light while maintaining a sufficient amount of light transmission.
As described, the anti-reflective coating does significantly reduce the reflection off the front surface of the lens of the prior art. However, anti-reflective coatings produce specular reflections of their own. For example, different types of anti-reflective coatings reflect in different colors, such as blue, green or red. The main purpose of nearly all anti-reflective coatings is to substantially eliminate white light reflection. If an anti-reflective coating is applied to a common dark lens, the result is that there will be a slight colored mirror effect, whether it be blue/purple, green or red. This is a common effect that can be seen on the backside of conventional sunglass lenses to which an anti-reflective coating has been applied. If an anti-reflective coating is applied to a clear uncolored lens, such as a lens used in a reading glass, the colored reflection is less obvious because light is easily transmitted from the wearer's side of the lens to the observer's side of the lens, thus washing out the specular reflection of the anti-reflective coating. In the case of a matte finish lens, in which the reflection is highly diffused, the specular reflection of the anti-reflective coating is readily apparent in incident light, which detracts from the desired effect of the lens. The only way to overcome and effectively compensate for the inherent reflection of the anti-reflective coating is to increase the brightness of the reflective medium, which, as previously described, caused difficulties in terms of reduced light transmission and increased back reflection.
The brushed finish was to found to be very problematic but for different reasons. While the brushed finish reflects brightly, it exhibits a more serious problem of internal reflection. The brushed finish incorporated in the lens construction of the prior art is defined by scratch lines or grooves that are generally linear and generally parallel to one another. The brushed finish reflects light in a bi-directional manner, meaning that it reflects light predominantly in two directions perpendicular to the grooved or scratch lines defining the brushed finish. This lens construction, as worn in an eyewear frame, produces a very sharp reflection within the lens viewable by the wearer whenever facing a bright light source such as the sun. The reflections can be so pronounced that one needs only to be facing in the general direction of the sun to have a spire like reflection, corresponding to the bi-directional reflective appearance of the lens, come into view. The appearance from a wearer's point of view is similar to that of an oily smear on the surface of a lens when viewed in direct light. Many variations were tested with practically no success in overcoming the internal reflections attributed to the brushed finish. It was found that the more parallel the scratches, or grooves, defining the brushed finish were, the more intense and pronounced the internal reflection. In an effort to reverse the problem, the scratch lines, or grooves, defining the brushed finish were made to be more divergent, or less parallel, by crisscrossing them in varying degrees. The more divergent the brushed lines were made to be the wider the reflection fanned out from the point where incident light strikes the surface of the lens as viewed from an observer's point of view. Correspondingly, the internal reflection affected a greater surface area of the lens, as viewed from a wearer's point of view. Different types of reflective mediums as well as improved anti-reflective coatings were tried. In all cases internal reflections remained, though in varying degrees, none of which proved satisfactory. Essentially, it was found that a lens construction having a bi-directional reflecting brushed finish highlighted by a reflective medium encapsulated within a lens construction inherently produces distracting internal reflections. The reflection, as viewed by an observer, generated by the brushed finish posed yet another problem. As previously stated, the brushed finish reflects brightly but because it reflects bi-directionally, when in bright light, unless properly positioned relative to the brushed finished lens and a given light source, a direct reflection from the reflective medium will not be apparent to an observer which in turn makes it more easy for an observer to see the eyes of the wearer. As with the matte finish lens of the prior art, the brushed finish lens was designed to cause the majority of the reflected light to come from the encapsulated reflective medium within the lens. Therefore, if the reflection produced by the reflective medium is unobserved or is not sufficiently bright, light is more easily transmitted from the wearer's side of the lens to the observers side of the lens, thus canceling any reflection produced by the reflective medium and making it easier for an observer to see through the lens to the eyes of the wearer. The resulting lens constructions of this prior art demonstrated that the brushed finish and the matte finish provided inherently poor optics in that they both exhibited poor reflective characteristics and, primarily in the case of the brushed finish, caused severe internal reflections. In order to increase the light transmission of the matte finish lens construction, the amount of reflective medium had to be reduced, which further reduced its reflective characteristics. In order to reduce the severity of the internal reflections of the brushed finish lens construction, the amount of reflective medium had to be reduced, thereby further reducing its reflective characteristics. The combination of optical performance and reflectivity must be properly balanced and that in order to do so and meet the design criteria set forth in the current invention a new type of reflecting surface must be provided for.